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All applicants are required to develop and submit a storm water management plan prepared by a professional engineer licensed in the state of Rhode Island. All storm water management plans must address storm water management on a site-by-site basis and all requirements of this chapter. All storm water management practices shall be consistent with the Rhode Island Storm Water Design and Installation Standards Manual and the Rhode Island Soil Erosion and Sediment Control Handbook, as amended. (1)
Performance standards. Storm water management plans shall incorporate structural and non-structural best management practices (BMPs) for water quality control, in accordance with Rhode Island Storm Water Design and Installation Standards Manual. Development in chinking water supply watersheds or watersheds where impaired waters as defined by the state's 303(d) list exist may be held to higher standards.
(2)
Disallowed storm water best management practices. The placement of storm water structures within a flood plain shall be avoided. If there is no alternative, the applicant must show what effects, if any, the tailwaters created by the flood plain will have on the outflow and effective storage capacity of the storm water best management practice.
(3)
Facilitation of maintenance. Facilities that require maintenance shall be designed to minimize the need for regular maintenance, facilitate required maintenance, and ensure accessibility of components that require maintenance. At a minimum, all storm water management plans must incorporate BMPs with appropriate maintenance design in accordance with the Rhode Island Storm Water Design and Installation Standards Manual, as amended.
a.
Control and maintenance of post-development peak discharge rates from the 2-year, 10-year, 25-year, and 100-year storm events to pre-development levels.
b.
Downstream analysis of the 100-year storm event and control of the peak discharge rate for the 100-year storm to mitigate downstream impacts.
c.
Discharge from any storm water facility must be conveyed through properly constructed conveyance system to provide for non-erosive flows during all storm events. The proposed storm water conveyance system consisting of open channels, pipes, and other conveyance devices shall at a minimum accommodate the runoff from a 25-year storm event. The storm water conveyance system must provide for non-erosive flows to receiving waters.
(4)
Flood protection. Storm water management plans shall demonstrate that a proposed project provides for protection of life and property from flooding and flood flows. Water quantities must be controlled in accordance with the Rhode Island Storm Water Design and Installation Standards Manual, as amended, or a municipally approved regional storm water management plan for the watershed in which the project site is located. Storm water management plans shall demonstrate incorporation of the following standards into the proposed project:
(5)
Surface water and groundwater. Storm water management plans shall, in accordance with the Rhode Island Storm Water Design and Installation Standards Manual, as amended, demonstrate that during development and post-development, all receiving waters will be recharged in a manner closely resembling pre-development conditions and that the developed site will retain hydrological conditions that closely resemble of those prior to disturbance. The goal of the storm water design shall be that hydrologic conditions in each sub-watershed match pre-development conditions.
Where practicable, development and re-development projects should aim to reduce runoff volumes. This may include minimizing and eliminating impervious surface areas such as roads, parking, paving or other surfaces, encouraging infiltration of a non-contaminated runoff, preventing channelization, encouraging sheet flow, and where appropriate, preserving, enhancing or establishing buffers along surface water bodies and tributaries.
(Ord. No. O-16-17, § I(Exh. A), 8-17-16)